The present invention relates to a multiplex transmission system, and in particular to a transmission system efficient for transmitting digital-coded audio signals, and the like, multiplexed on video signals, and to a signal generation apparatus and signal regeneration apparatus for such transmissions.
In the past, a method for transmitting digital-coded audio signals (hereafter referred to as PCM audio signals) multiplexed on video signals was reported in T. Arai, et al.: Receiver for DBS with Digital Audio Signals, IEEE TRANS., CE-30 No. 3 (Aug. 1984). The contents of this report will now be described. A subcarrier of 5.7272 MHz is multiplexed on a video signal of a NTSC system ranging to 4.2 MHz by using different frequencies. The subcarrier is QPSK-modulated by PCM audio signals. In this system, however, the subcarrier frequency is located outside the band of current television. Therefore, it is impossible to put this system in force while assuring compatibility with current television.
A method for multiplexing another signal onto current television is described in Broadcasting Technical Library 2 "Broadcasting System" edited by the Japan Broadcasting Corporation and published by the Japan Broadcasting Publication Corporation in January 1983, pp. 205 to 208. However, a system for obtaining a transmission rate not less than approximately 1M bits/second, which is required to transmit high quality PCM voices, is not described.
In the above described prior art, transmission of signals having a transmission rate of approximately 1 M bits/sec multiplexed on a current television signal was not considered. Accordingly, there was a problem that multiplex transmission of high quality PCM voices was impossible.